1. Field of the Invention
The present invention relates to an outboard motor. In particular, the present invention relates to an outboard motor including an engine cover provided with an outside air inlet and an intake device supplying combustion air to an engine.
2. Description of the Related Art
There are known various techniques for preventing water mixed in combustion air from intruding into a combustion chamber in an outboard motor including an internal combustion engine housed in an engine room formed by an engine cover. In particular, the internal combustion engine mounted on a propulsion unit such as the outboard motor or the like is required to have a compact and excellent function of preventing intrusion of water.
Conventionally, for example, outboard motors described in Patent Documents 1, 2 and so on are configured such that when water is mixed in the combustion air flowed therein from the intake port of the intake passage, the water is separated from the combustion air by the centrifugal force in an inversion flow passage for the purpose of improving the effect of preventing intrusion of water into the combustion chamber of the internal combustion engine and the efficiency of filling the intake air. It is also intended to suppress heated air flowing into the engine room from the intake port of the intake passage to suppress an increase in temperature of the combustion air so as to improve the filling efficiency.
Patent Document 1: Japanese Laid-open Patent Publication No. 2008-88881
Patent Document 2: Japanese Laid-open Patent Publication No. 2007-8416
Incidentally, in the outboard motor described in Patent Document 1, the outside air inlet of an outside air intake space formed by an exterior cover is opened to face rearward, namely, in an opposite direction to the forward direction of the outboard motor. In the outboard motor, regarding in particular intake air, air is taken in against the flow of the air flowing outside the outboard motor. In such a way of taking the intake air, an intake resistance occurs to reduce the intake efficiency, resulting in a decrease in engine output.
Meanwhile, regarding only this point, it is possible to provide the outside air inlet to face forward in order to improve the intake efficiency. However, if the outside air inlet is disposed to face forward in this manner, the spray of water or the like enters from the outside air inlet during traveling of the boat, so that the intake structure cannot be actually realized.
Further, the air taken into the engine cover flows immediately near the engine at a high temperature and is thus heated, and is then sucked into the throttle body and fed to the combustion chamber. The heated intake air is low in filling efficiency (volumetric efficiency), causing problems of affecting the combustion efficiency and further the fuel cost and so on.